The present invention pertains in one aspect to a method of removing fat-protein residues from a starch hydrolysate solution containing same. In another aspect, such invention pertains to methods or processes for the hydrolysis of a granular starch material to glucose. In yet another aspect, this invention relates to a method for separating fat-protein residues from a granular starch material having said fat-protein residues adsorbed, coated or otherwise deposited upon the surface thereof and for converting said granular starch material to maltodextrin, syrups and/or glucose.
In the manufacture of starch hydrolysate materials such as maltodextrin, syrups, glucose, etc. from a granular starch feedstock, it is conventional practice to first subject an aqueous slurry of said granular starch material to a cooking or pasting operation, which is typically conducted at a temperature of from about 90.degree. to about 180.degree. C., and to thereafter convert the resulting cooked or pasted starch material to the desired starch hydrolysate product (e.g., typically maltodextrin, syrup or glucose) via one or more acid and/or enzyme hydrolysis operations.
In the case of enzyme-based hydrolysis operations, the cooked or pasted starch is typically treated for a relatively short period of time (e.g., 1 to 4 hours) under mildly acidic conditions (e.g., generally at a pH of about 6) and at a relatively high temperature (e.g., up to about 115.degree. C.) with thermostable alpha-amylase enzyme in order to convert said starch slurry to maltodextrin. Such treatment is generally referred to in the art as the "thinning" reaction. In the event that the maltodextrin thus formed is the desired end-product, the crude hydrolysis reaction product is purified by removing the fat and/or protein (also referred to herein as fat-protein) liberated from the granular starch material during the cooking or pasting operation via a conventional separation technique such as filtration, centrifugation etc. The fat and/or protein material liberated and removed in this fashion is commonly referred to in the art as "mud".
On the other hand, if the desired ultimate end-product is syrup or glucose, the aforementioned maltodextrin material is subjected to further hydrolysis to convert said maltodextrin material (typically having a dextrose equivalent, D.E., of from about 1 to about 25 and preferably from about 5 to about 15) to the desired syrup or glucose product. This latter hydrolysis operation is commonly referred to in the art as a "saccharification" process or operation. When said saccharification operation is performed via acid hydrolysis techniques, it is typically conducted using a strong mineral acid such as hydrochloric or sulfuric acid; at a pH in the range of from about 1 to about 2; at a temperature in the range of from about 90.degree. to about 180.degree. C.; and for a time period or reaction time of from about 0.1 to about 2 hours. Alternatively, when said saccharification process is performed via an enzyme hydrolysis reaction, it is generally conducted using glucoamylase enzyme at a pH of about 4 to about 5; at a temperature of approximately 60.degree. C.; and for a reaction period of from about 24 to about 96 hours.
In those instances wherein the maltodextrin material is further hydrolyzed to glucose or syrup, the removal of fat and/or protein materials released or liberated from the granular starch feedstock during the cooking operation and/or during the initial hydrolysis (e.g. "thinning") operation is conventionally conducted either prior to, during or after the maltrodextrin-to-syrup or glucose hydrolysis operation using conventional separation techniques such as centrifugation, filtration and the like.
The foregoing techniques are generally capable of converting granular starch slurries to maltodextrin, syrup or glucose as desired and, indeed, they find relatively widespread commercial application for such purpose. However, such techniques are nonetheless still hampered by certain drawbacks or disadvantages. For example, the cooking or pasting operation and the initial starch-to-maltodextrin hydrolysis (or "thinning") operation are both conducted at relatively high temperatures and are therefore relatively energy intensive (and expensive) in character. In addition, the two different hydrolysis operations employed (i.e., starch-to-maltodextrin in the one instance and maltodextrin-to-syrup or glucose in the other) are generally conducted at different pH's and therefore require the addition of chemical reagents for pH adjustment purposes along with the attendant need to ultimately remove such reagents from the desired hydrolysate product. Moreover, the aforementioned maltodextrin-to-syrup or glucose enzyme hydrolysis operation (e.g., "saccharification" using glucoamylase enzyme at about 60.degree. C. and a pH of about 4) is a relatively slow reaction requiring relatively long reaction times and thereby inherently placing significant limitations upon the ultimate production capacity of any given-sized manufacturing facility and/or reaction vessel. Accordingly, it would be highly desirable to provide a method for the hydrolysis of starch to maltodextrin, syrup and/or glucose which would minimize the aforementioned drawbacks and disadvantages.
In addition to the foregoing, it has also been observed that the conventional techniques (e.g., filtration and/or centrifugation) for removing liberated fat and/or protein during the aforementioned hydrolysis operations are oftentimes not as effective as might be desired in accomplishing their stated purpose and that, as a result, an undesired fat and/or protein build-up may occur over prolonged periods. This can be a highly undesirable development for several reasons. For example, the built-up fat and/or protein material may ultimately degrade within the saccharification reactor and the resulting degradation products may substantially reduce the quality of the desired starch hydrolysate product. Further, fat and/or protein in the saccharified product can foul ion exchange resins employed in downstream refining operations and can also cause the resulting hydrolysate product to be hazy or to have undesirable flavor components. Accordingly, it would be highly desirable to provide an improved method of removing fat and/or protein materials from starch hydrolysate solutions.
As an alternative to the above-described conventional starch hydrolysis methodology (i.e., involving first cooking or pasting a raw granular starch slurry feedstock followed by one or more subsequent enzyme and/or acid hydrolysis treatments), it has also been suggested to develop and employ enzyme hydrolysis processes capable of hydrolyzing a raw granular starch feedstock directly to maltodextrin and/or glucose at relatively low temperatures and without the starch feedstock first having been subjected to an initial cooking or pasting operation. See in this regard U.S. Pat. Nos. 3,922,196 and 3,922,197 to Leach et al.; 3,922,198 to Kuske et al.; 3,922,199 and 3,922,201 to Hebeda et al.; and 3,922,200 to Walon et al. (all of which issued on Nov. 25, 1975) for representative art pertaining to this latter technique or approach. Unfortunately, this type of approach is also not without certain drawbacks or disadvantages and is thought to have thus far not found commercial acceptance or applicability. For example, while certain enzyme systems have been proposed as being capable of directly hydrolyzing raw, granular starch material to maltodextrin, syrup and/or glucose, as a practical matter none proposed to date appear to have the capability of doing so at a commercially viable combination of yield, reaction rate and dry solids content. As such, it would be highly desirable to provide an efficient and effective method for the direct enzyme hydrolysis of a raw granular starch slurry feedstock to starch hydrolysate products such as maltodextrin, syrups, glucose and the like.